The present invention relates generally to a meter drive circuit and, more particularly, to an inhibit circuit for use in a meter drive circuit.
In an electronic meter such as a tachometer or speedometer, a pulse generator is utilized to provide an output pulse at a frequency related to the rate of rotation of an appropriate shaft in the vehicle in which the meter is mounted. Such a pulse generator usually comprises a general purpose integrated circuit which receives a triggering pulse from a sensor circuit associated with the rotating shaft. The output from the pulse generator is usually a series of squarewave pulses which are supplied to a meter drive circuit. This meter drive circuit can take many forms, but typically comprises a semiconductor device which in turn is connected to the actual meter. The meter usually comprises an electromechanical meter having a needle movement whose deflection is related to the time average value of the pulse input from the meter drive circuit.
A problem with such electronic meters is that the pulse generator may provide an unwanted output pulse upon turning on or power-up of the device. Such an unwanted pulse would cause the meter needle to jump to an erroneous high value and then fall back to a zero value. This is an undesirable condition, and accordingly, it is an object of the present invention to provide a meter drive inhibit circuit to prevent such erroneous meter pointer movement.